The present invention relates to a blade row, in particular a guide vane assembly or rotor assembly, for a turbomachine, in particular a gas turbine, and a turbomachine having at least one such blade row.
Known blade rows are composed of a plurality of blade arrangements each having one or more blades. To increase the stability of such a blade row and/or guide a working fluid, arranging shrouds on the blade tip is known, i.e., for rotor blades on the radial outside and for guide blades on the radial inside, wherein shrouds of adjacent blade arrangements contact each other in a braced manner.
Especially in the case of a loss of shroud bracing, for example after a long operating time or due to a fault, the blades may become aeroelastically unstable and flutter, which may lead to fatigue failure of the blades.
Therefore, arranging first and second blade arrangements with shrouds in an alternating manner is known from GB 252,701 B1, wherein the blades of adjacent blade arrangements have different blade profiles and the shrouds of adjacent blade arrangements have different radial wall thickness so that adjacent blade arrangements have different natural frequencies. However, in order to produce greater frequency differences in this case, the radial wall thickness would have to vary greatly. However, this would produce a greatly varying outside surface of the shroud bond in the radial direction, which can be disadvantageous dynamically and/or fluidically.
The object of the present invention is making an improved blade row available.
A blade row, according to the present invention, has a number of first blade arrangements. The number may be one or more and is even or odd in a preferred further development. The first blade arrangements each have one or more first blades and a first shroud, which, in a preferred further development, is firmly connected to the blades, in particular configured integrally with the blades. Similarly, the shroud may also be detachably connected to the blades. On the side which radially opposes the shroud, the blade(s) preferably have a blade platform, which, in a preferred further development, is firmly connected to the blades, in particular configured integrally with the blades. A blade arrangement within the scope of the present invention is therefore defined in particular by a shroud which is connected to the blade(s) of the blade arrangement.
The shrouds of the first blade arrangements each have an extension in the circumferential and axial direction; these first shrouds are preferably annular, at least substantially.
The blade row has at least a number of additional blade arrangements. This number may likewise be one or more and is even or odd in a preferred further development. Additional blade arrangements each have one or more additional blades and an additional shroud, which, in a preferred further development, is firmly connected to the blades, in particular configured integrally with the blades. Similarly, the shroud may also be detachably connected to the blades. On the side which radial opposes the shroud, the blade(s) preferably have a blade platform, which, in a preferred further development, is firmly connected to the blades, in particular configured integrally with the blades. An additional blade arrangement preferably corresponds to a first blade arrangement except for the differences explained in the following.
According to the invention, the extension of the additional shrouds is different in the circumferential and/or axial direction from the extension of the first shrouds in this direction. The additional shrouds, which are preferably likewise annular, at least substantially, may therefore be longer or shorter than the first shrouds particularly in the circumferential direction and in particular have different overhangs in the circumferential direction. In addition or as an alternative, the additional shrouds may be longer or shorter in the axial direction than the first shrouds and in particular project over or be set back from the edges of the first shrouds in the axial direction on one or both sides.
This makes it possible, preferably in the case of an at least substantially radially homogeneous outside lining of the shroud bond of the blade row, to produce different natural frequencies of the first and additional blade arrangements and thereby reduce an aerodynamic vibration, in particular in the case of the loss of a shroud bracing. In a preferred further development, the extension in the radial direction may also be different from the first shrouds and additional blade arrangements, wherein preferably, in the case of a rotor assembly, a radially unchanging or annular outer outside lining is provided and, in the case of a guide vane assembly, a radially unchanging or annular inner outside lining is provided.
In addition to an additional blade arrangement, whose additional shrouds have different extensions than the shrouds of the first blade arrangements, the blade row may have one or more numbers of other additional blade arrangements, whose other additional shrouds have an extension in the circumferential, axial and/or radial direction that is different from the corresponding extension of the other blade arrangements, in particular the first and the additional blade arrangements. Therefore, especially a number of first blade arrangements, an equal or other number of additional second blade arrangements and preferably an equal or other number of other additional third blade arrangements may be provided. In addition, an equal or other number of other additional, fourth blade arrangements may be provided, an equal or other number of other additional, fifth blade arrangements may be provided and so forth. In the process, extensions of shrouds of additional or other additional blade arrangements may be different from each other in the circumferential, axial and/or radial direction and/or from the extensions of the first shrouds. For example, the additional shrouds of additional, second blade arrangements may be shorter or longer in the circumferential direction than the first shrouds. The additional shrouds of other additional, third blade arrangements may be shorter or longer in the circumferential direction than the additional shrouds and preferably also than the first shrouds. In addition or as an alternative, the additional shrouds of additional, second blade arrangements may be wider or narrower in the axial direction than the first shrouds. The additional shrouds of other additional, third blade arrangements may be wider or narrower in the axial direction than the additional shrouds and preferably also than the first shrouds.
In a preferred embodiment, an additional extension, i.e., an extension of a shroud of an additional or one other additional blade arrangement is larger or smaller in the circumferential, axial, and/or radial directions by at least 10%, preferably by at least 15% and preferably by at least 20% than the first extension of a shroud of a first blade arrangement and/or one other additional extension of a shroud of one other additional blade arrangement. In particular, the extensions of adjacent shrouds may be disposed in opposite directions in the circumferential and axial directions, i.e., in the axial direction, wider shrouds are adjacent to narrower shrouds, which, however, are longer in the circumferential direction so that differences in mass are reduced; however, due to the different moments of inertia around the blade axes, the natural frequencies are detuned.
In a preferred embodiment, the shrouds of one or more, preferably all, blade arrangements are symmetrical to the blades of this blade arrangement in the circumferential and/or axial direction. Symmetry in the axial direction should be understood in particular to mean that the shrouds or blades project by the same amount in the axial direction on both sides, and symmetry in the circumferential direction correspondingly means that the shrouds or the blades overhang by the same amount in the circumferential direction. Similarly, the shrouds of one or more, preferably all, blade arrangements may also be asymmetrical to the blades of this blade arrangement in the circumferential and/or axial direction. In particular, shrouds may be offset from the blades of the blade arrangements in the circumferential and/or axial direction, or project or overhang on both sides of the blade arrangement by different amounts.
In a preferred embodiment, two or more, in particular all blade arrangements have the same number of blades; in a preferred further development each have precisely one blade. As explained in the foregoing, one (other) additional blade arrangement preferably corresponds, except for the extension of the shrouds, to the first blade arrangement.
In a preferred embodiment, the first and one additional, in particular all additional, blade arrangements are distributed cyclically over the circumference. If the blade row has a number of first and only a number of additional blade arrangements, they are distributed in an alternating manner over the circumference. If the blade row has a number of first blade arrangements, a number of additional, second blade arrangements, and a number of additional, third blade arrangements, in the case of a cyclical distribution, they may be distributed over the circumference, for instance in the sequence of first blade arrangement, second blade arrangement, third blade arrangement, first blade arrangement; or in the sequence of first blade arrangement, second blade arrangement, first blade arrangement, third blade arrangement, first blade arrangement.
In a preferred embodiment, shrouds of adjacent blade arrangements have complementary, in particular non-planar, contact surfaces facing each other. The contact surfaces may be configured to be undulated in particular. By designing the contact surfaces of different shrouds to be different, it is possible to ensure a predetermined distribution of the blade arrangements during assembly.
In a preferred embodiment, shrouds of at least one blade arrangement have one or more recesses or pockets, wherein shrouds of at least one other blade arrangement have no recess. In addition or as an alternative, shrouds of at least one other blade arrangement, have another number, arrangement and/or shape of recesses. Through this, the natural frequencies of the blade arrangements are also able to be detuned.
Additional features and advantages are disclosed in the subordinate claims and exemplary embodiments.